I used to tell my students, "Colour has only two attributes or
properties, physical and psychological. We can re-name them,
measure and pleasure."
Our sensitivity to color derives from the sensitivity of the rods and
cones on the surface of the retina in the eye to energies of wavelength
400nm (blue) to 700nm (red). So when we measure color we record
the way in which the particles in the object have interacted with the
energy. If all of the energy is absorbed, the object appears
black. If all of the energy is reflected, the object
appears white. If some of the energy is absorbed, the
object appears coloured.
So when you “see” an object, your eyes are stimulated by the waves of
energy coming from the object. The wavelength and frequency of
theses waves determines the “color” that you “see”.
We cannot synthesize color easily. In print or on the screen, we
rely on the model of the physicist James Clerk Maxwell, who suggested
that we could synthesize from the addition of varying amounts of Red,
Green and Blue light.
There have been many ways in which people have suggested that color
can be made from RED GREEN and BLUE. The next image from
http://www.codeproject.com is one such method devised by Albert
Munsell, called the Munsell Colour Wheel.
Using 3D co-ordinates a color can be defined. The definition is made in terms of hue
(color), chroma (saturation), and value (amount of black and white
added). This is a measure of “pleasure of color”.
The Munsell system defines color along these three measurement axes.
Black and white and grey are not colors. They are brightness
values or modifiers. They are modifiers for the colors into
which they are mixed, or onto which they have been layered.
However the color you get in your camera sensor; your RAW file; your
post-processing software; your monitor; your print, are all different
because of the way in which the color is synthesized and defined by
the software. This is “color space” or gamut.
Gamut
is
based on the ICI System of colour definition ( ICI - an organization
who defined color in this way. I assume chemical company for
dyes.). This is defined in
terms of the dominant wavelength, excitation purity and luminous
intensity. This is a measure of “measure of colour”.
Gamut - is this representation of these definitions in a 2D or 3D
space, mathematically speaking. No two Gamuts are the same.
The gamut for a monitor is a smaller space than PANTONE inks so you get
a wider range of color in your printed images using PANTONE inks that
you can see on your monitor.
color In
Your Software
Color is a property of all objects, and it is one of the properties
that designers and advertisers use to draw your eye to the object.
In Paint Shop Pro or your photo processing software, call up a new page
on which to paint, select a brush with which to paint and open the color
dialogue box.
Manually, type in the values of Red (255), Green (0),
andBlue (0). Now
adjust the values to Red
(255), Green
(255) and Blue (0). When
you change the values the foreground color changes.
The color changes from red to yellow. In this way we
can fool ourselves that we have made over 16 million colors. And
in that assumption belies our first and major problem. We cannot
guarantee that the color we print matches the color we chose on the
VDU - and - we cannot guarantee that the color we see on the VDU
matches the color we saw in the original scene.
You can check the color synthesis of any part of your image by moving
the mouse or tablet pen over the image, and the RGB values are shown in
the bottom of the screen. The values show the color value under
your pen or mouse.
In the Watercolour
Tutorial, I
wanted to emphasize the red in the figure to the left hand edge.
Red is a color which always wants to come to the fore. Using the
WACOM tablet and pen on the masking layer, I was able to enhance the
red and make it really advance towards me.
Blue, which we always
associate with sky, is recessive. We use this distinction to give
us information about depth and distance. Green is seen as the
colour of vegetation and tranquility. It comes as no surprise
that the middle of the spectrum visible to us, is green, and is the color to which our eyes have the greatest sensitivity.
The Color Wheel
The color wheel is one way in which we try to make sense of color
associations. colors opposite to one another on this wheel have
particular dynamism if close together in an image.
If you look in Paint Shop Pro at Adjust > Hue and Saturation
> Hue/Saturation/Lightness you can see the color wheel
representation being used.
So, blue and yellow are opposites, cyan (turquoise) and red, green and
magenta (purple). Fashionistas will tell you never to wear
clothes that are color opposites because of this color
dynamism. But then, the dynamism can be used to pull attention in
your photographs.
Any pair of colors directly opposite each other in the color wheel show
this dynamism. If we place the colors against each other, as in
the square below, we can see their visual inmpact on each other.
Notice that intersecting lines from opposite sides of the wheel seem to
“jar”.
I've marked the intersection which are opposite pairs.
When dyers, printers and serious photographers try to reproduce color,
they use spectrophotometers to measure reflectance, and balanced light
sources to compare samples in grey painted environments to prevent any
influence from the surroundings. As you attempt to print color,
the next set of problems arise.
color dyes in inkjet printers
and conventional photographic paper have limited archival lifetimes.
Pigments although they are less light sensitive, are less easily
applied.
Only if you are trying to perfectly color match the print with the
original image do you need to consider the attribute of measure.
Most of the time, the attribute pleasure comes into play.
Choose
a well lit, strongly colored object and stare at it for at least 30
seconds. Close your eyes and you will “see” the object but as a
negative image; so a blue bath towel on the washing line will appear
yellow in your mind when you’ve closed your eyes.
Yellow is the
complementary color to blue.
Your brain reduced the value of the
image in your brain, compensating for the color and the colours around
it. When you close your eyes the compensation remains, ie a
yellow image. For that reason you see the objects in a
fluorescent lit room as normal; but really the room has an abundance of
green light from the light source.
It’s only when you look at the
photos you took that you see the incorrect rendering unless, of
course, you set the white balance correction in the camera! But
then you might set the White Balance to warm or cool the image, again
this is all to do with mood.
